The present invention relates to a method for treating benign prostate hyperplasia (BPH) and, more particularly, to a method devised for cryoablating BPH through the urethra, yet minimizing the damage inflicted upon urethral tissue in course of treatment.
BPH, which affects a large number of adult men, is a non-cancerous enlargement of the prostate. BPH frequently results in a gradual squeezing of the portion of the urethra which traverses the prostate, also known as the prostatic urethra. This causes patients to experience a frequent urge to urinate because of incomplete emptying of the bladder and a burning sensation or similar discomfort during urination. The obstruction of urinary flow can also lead to a general lack of control over urination, including difficulty initiating urination when desired, as well as difficulty in preventing urinary flow because of the residual volume of urine in the bladder, a condition known as urinary incontinence. Left untreated, the obstruction caused by BPH can lead to acute urinary retention (complete inability to urinate), serious urinary tract infections and permanent bladder and kidney damage.
Most males will eventually suffer from BPH. The incidence of BPH for men in their fifties is approximately 50% and rises to approximately 80% by the age of 80. The general aging of the United States population, as well as increasing life expectancies, is anticipated to contribute to the continued growth in the number of BPH sufferers.
Patients diagnosed with BPH generally have several options for treatment: watchful waiting, drug therapy, surgical intervention, including transurethral resection of the prostate (TURP), laser assisted prostatectomy and new less invasive thermal therapies.
Currently, of the patients suffering from BPH, the number of patients who are actually treated by surgical approaches is approximately 2% to 3%. Treatment is generally reserved for patients with intolerable symptoms or those with significant potential symptoms if treatment is withheld. A large number of the BPH patients delay discussing their symptoms or elect "watchful waiting" to see if the condition remains tolerable.
The development of a less invasive treatment for BPH could result in a substantial increase in the number of BPH patients who elect to receive interventional therapy.
Drug Therapies:
Some drugs are designed to shrink the prostate by inhibiting or slowing the growth of prostate cells. Other drugs are designed to relax the muscles in the prostate and bladder neck to relieve urethral obstruction. Current drug therapy generally requires daily administration for the duration of the patient's life.
Surgical Interventions:
The most common surgical procedure, transurethral resection of the prostate (TURP), involves the removal of the prostate's core in order to reduce pressure on the urethra. TURP is performed by introducing an electrosurgical cutting loop through a cystoscope into the urethra and "chipping out" both the prostatic urethra and surrounding prostate tissue up to the surgical capsule, thereby completely clearing the obstruction. It will be appreciated that this procedure results in a substantial damage inflicted upon the prostatic urethra.
Laser Ablation of the Prostate:
Laser assisted prostatectomy includes two similar procedures, visual laser ablation of the prostate (V-LAP) and contact laser ablation of the prostate (C-LAP), in which a laser fiber catheter is guided through a cystoscope and used to ablate and coagulate the prostatic urethra and prostatic tissue. Typically, the procedure is performed in the hospital under either general or spinal auesthesia, and an overnight hospital stay is required. In V-LAP, the burnt prostatic tissue then necroses, or dies and over four to twelve weeks is sloughed off during urination. In C-LAP, the prostatic and urethral tissue is burned on contact and vaporized. Again, it will be appreciated that these procedures result in a substantial damage inflicted upon the prostatic urethra.
Heat Ablation Therapies:
Other technologies under development or practice are non-surgical, catheter based therapies that use thermal energy to preferentially heat diseased areas of the prostate to a temperature sufficient to cause cell death. Thermal energy forms being utilized include microwave, radio frequency (RF) and high frequency ultrasound energy (HIFU). Both microwave and RF therapy systems are currently being marketed worldwide. Heat ablation techniques, however, burn the tissue, causing irreversible damage to peripheral tissue due to protein denaturation, and destruction of nerves and blood vessels. Furthermore, heat generation causes secretion of substances from the tissue which may endanger the surrounding area.
Transurethral RF Therapy:
Transurethral needle ablation (TUNA) heats and destroys enlarged prostate tissue by sending radio waves through needles urethrally positioned in the prostate gland. The procedures prolongs about 35 to 45 minutes and may be performed as an outpatient procedure. However TUNA is less effective than traditional surgery in reducing symptoms and improving urine flow. TUNA also burn the tissue, causing irreversible damage to peripheral tissue due to protein denaturation, and destruction of nerves and blood vessels. Furthermore, as already discussed above, heat generation causes secretion of substances from the tissue which may endanger the surrounding area.
Cryoablation Therapy:
During conventional cryoablation therapy part of the prostate gland is frozen by pencil like probe placed into the gland through the perineum, an ultrasound is used throughout the procedure to monitor the progress of the freezing. The limitations of this procedure are its invasiveness.
There is thus a widely recognized need for, and it would be highly advantageous to have, a method for cryoablating BPH through the urethra, yet minimizing the damage inflicted upon urethral tissue in course of treatment and which is devoid of the above limitations associated with prior art techniques.